1. Field of the Invention
The present invention relates to a permanent magnet rotor (hereinafter, referred to also simply as the rotor) formed by inserting a permanent magnet (hereinafter, referred to also simply as the magnet) into a rotor of an electric motor.
2. Background Art
To obtain a permanent magnet rotor by inserting a permanent magnet into an internal slot of an electric motor rotor and fixing the magnet therein, an adhesive, such as epoxy resin, may be applied between the internal slot and the magnet and cured to fix the magnet. However, this method requires a thermal curing process to cure the adhesive and admits of improvement in terms of mass-production. As an alternative, there is proposed a method that eliminates the need of a complex process by providing a groove in an inner peripheral portion of the internal slot and inserting a magnet fixing metal split pin into the groove after a permanent magnet is inserted into the slot. An example is described in Patent Document 1.    Patent Document 1: JP-A-5-83892
The structure of Patent Document 1, however, may damage the magnet because the metal split pin hits against the magnet when the magnet and the split pin vibrate due to resonance. Because the electric motor incorporated into an automobile, in particular, undergoes vibrations of the vehicle and the engine, it is preferable to reduce vibrations of the magnet. Vibrations may be reduced by inserting a buffer member, such as rubber, instead of the metal split pin. Strong friction of the rubber, however, makes it difficult to press-fit the rubber into the slot. This alternative therefore requires an arrangement to insert the rubber while letting the rubber undergo elastic deformation by applying an external force to the rubber and has a problem that the process becomes complex.